Strange double buffering bug

Hi all,
I have stumbled on strange swing behavior on Windows, most probably connected to double buffering introduced in java 6.
Once in a while Windows stops redrawing my JFrame. From the java side everything seems ok - all the components are painted (that is, all native methods called), EventQueue normally processed by EDT, but repainted GUI is not shown on the screen. Note that OS has the repainted info - if I cover part of the application window with another window (e.g. explorer), and hid it back, the part that was covered is repainted. This happens even if I have java app halted on debug, so no other java actions can cause this repaint - OS has to have this image, it just does not put it on the screen. When I minimize/maximize the app, everything goes back to normal.
Note that I can normally operate the app "as if" it was painted - I can change tabs, click buttons (even though I can't see them), and results of these actions are painted by java to some offscreen buffer, but are only shown when I cover/uncover my app with another window, or min/max it. Min/Maxing ends this strange state and further repaints are shown normally.
Did any of you have this kind of problem? Any idea how to approach/resolve it or what can be the cause?
Java is 1.6.20, I have seen the behavior on Windows XP, Vista and 2008. It is not reproducible, it just happens sometimes. I haven't seen that on Java 5. Turning off double buffering resolves that, but is not feasible due to degraded user experience.
Thanks in advance for your help!
Jakub

Thanks for your help so far, perhabs this is something with the driver, but I use fairly generic windows distribution.
EDT is not hosed, it is processing events normally (I checked that on debug step-by-step). We do not override any paint methods, and this is rather something on different level - it is not "a component not being repainted" it is "everything is repainted, but not shown on screen". Including tabbedPane's tab changes, menu display, etc. I can even see cursor changing into carret when I hover over "not shown" textfield.
Displaying and then disposing of modal dialog also fixes the state, as do resizing of the JFrame.

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Double buffering

I was searching through posts to find an answer to my problem of getting double buffering working without flickering when I came across this response:
Upgrade your SDK, early 1.4 implementations had this problem on Windows2k (It's a bug). Pretty much the second buffer will point to an empty portion of video memory always, the solution to this without updating is to fill the entire backbuffer completely, flip it, fill it again, and then flip it again. You should then be able to use it normaly.
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And here is the relevant code for my run method:
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Double buffering circle not round anymore

I am making an applet where some circles are painted to the screen. When not using the double buffering scenario, the shapes appear correctly.
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Ok, i had some problem with the running thread when closing the applet viewer, but now this situation is corrected by setting the animation thread to null before calling stop().
Maybe explanation of the problem is not clear, so i made two versions of the same applet with only 2 lines of code different so that there is one applet that is not double buffered.
You can check these by yourself at this place:
Double buffered circles: http://www.geocities.com/xeneve/cooltrail/ demo_cooltrail.htm
No double buffer:
http://www.geocities.com/xeneve/cooltrail/demo_cooltrail_ndb.htm
This is just annoying to get this result. I realise that maybe not many peoples are coding applets so i guess there is few people that may have a workaround for this.

Double buffering circle not round

I am making an applet where some circles are painted to the screen. When not using the double buffering scenario, the shapes appear correctly.
The problem is when i use the double-buffering technique, the circles are still there, but they look like very ugly. I would call that some "squarcles".
What is the bug here and how to get some decent double buffering with thoses circles?

Here is the code so far i have that is used for painting on the screen:
// Declaration
private BufferedImage ecran;
private Graphics2D buffer_ecran;
// Instantiation
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this.buffer_ecran = ecran.createGraphics();
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Graphics be = buffer_ecran;
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Double buffering issue

I have a complex modal JDialog with many JTextFields. Before it becomes visible I call setText("") on these fields to reset their values. When the dialog appears for the second time I see for a moment the old values of these fields. There is no such behaviour if I turn off double buffering on JRootPane of this dialog. Is it a bug or by design? It looks very ugly.
JDK 1.6.0.27, Linux 2.6.31

Here is an example. Click 'open', click 'fill values', close the dialog. Repeat until you see the old values in the JTextFields for a blink of an eye. Uncomment XXX to avoid this effect.
public class Test
    private static MyDialog dialog;
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                final JFrame frame = new JFrame();
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                JButton b = new JButton(new AbstractAction("Open")
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                frame.setVisible(true);
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        public MyDialog(Frame owner)
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            int n = 20;
            setLayout(new GridLayout(n + 1, 2));
            textFields = new JTextField[n];
            for (int i = 0; i < n; ++i)
                JTextField tf = new JTextField();
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            JButton b = new JButton(new AbstractAction("Fill values")
                @Override
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                    for (JTextField tf : textFields)
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            add(b);
        private void clear()
            for (JTextField tf : textFields)
                tf.setText("");
}

Need double buffering enabled if I print a JTable

Hi @ all
I have printed a very large JTable. The Problem is if I disable double
buffering the horizontal lines move after some pages.
If I enable double buffering the printout looks very bad(as all know).
But the horizontal lines are OK!
You can produce this failure with the print tutorial(and a large table).
Has someone an idea how I can fix my bug ?
many thanks for helping

may be you have to disable double buffering generaly to all the element envolved in the printing component, try this:
private void setDoubleBuffering(Component c, boolean isEnabled) {
RepaintManager manager = RepaintManager.currentManager(c);
manager.setDoubleBufferingEnabled(isEnabled);
}

Problem with Double Buffering and Swing

Hi
I made a game and basically it works pretty well, my only problem is it flickers really badly right now. I read up on a whole lot of forums about double buffering and none of those methods seemed to work. Then I noticed that Swing has double buffering built in so I tried that but then I get compilation errors and I'm really not sure why. My original code was a console application and worked perfectly, then I ported it into a JApplet and it still works but it flickers and thats what I'm tryign to fix now.
The code below is in my main class under the constructor.
Heres the double buffering code I'm trying to use, I'm sure you all seen it before lol
public void update(Graphics g)
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          g.drawImage(dbImage, 0, 0, this);
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This snipet of code works but when I change the method to
public paintComponent(Graphics g){
super.paintComponent(g)...
everythign stops working and get a compilation error and says that it can't find paintComponent in javax.swing.JFrame.
public void paint(Graphics g)
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               z_ufo.draw_shape(g);
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Thanks in advance
Sebastian

This is a simple animation example quickly thrown together. I have two classes, an animation panel which is a JPanel subclass that overrides paintComponent and draws the animation, and a JApplet subclass that simply holds the animation panel in the applet's contentpane:
SimpleAnimationPanel.java
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.JPanel;
import javax.swing.Timer;
class SimpleAnimationPanel extends JPanel
    private static final int DELAY = 20;
    public static final int X_TRANSLATION = 2;
    public static final int Y_TRANSLATION = 2;
    private Point point = new Point(5, 32);
    private BufferedImage duke = null;
    private Timer timer = new Timer(DELAY, new TimerAction());
    public SimpleAnimationPanel()
        try
            // borrow an image from sun.com
            duke = ImageIO.read(new URL(
                    "http://java.sun.com/products/plugin/images/duke.wave.med.gif"));
        catch (MalformedURLException e)
            e.printStackTrace();
        catch (IOException e)
            e.printStackTrace();
        setPreferredSize(new Dimension(600, 400));
        timer.start();
    // do our drawing here in the paintComponent override
    @Override
    protected void paintComponent(Graphics g)
        super.paintComponent(g);
        if (duke != null)
            g.drawImage(duke, point.x, point.y, this);
    private class TimerAction implements ActionListener
        @Override
        public void actionPerformed(ActionEvent e)
            int x = point.x;
            int y = point.y;
            Dimension size = SimpleAnimationPanel.this.getSize();
            if (x > size.width)
                x = 0;
            else
                x += X_TRANSLATION;
            if (y > size.height)
                y = 0;
            else
                y += Y_TRANSLATION;
            point.setLocation(new Point(x, y)); // update the point
            SimpleAnimationPanel.this.repaint();
}AnimationApplet.java
import java.lang.reflect.InvocationTargetException;
import javax.swing.JApplet;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class AnimationApplet extends JApplet
    public void init()
        try
            SwingUtilities.invokeAndWait(new Runnable()
                public void run()
                    // construct the panel
                    JPanel simpleAnimation = new SimpleAnimationPanel();
                    // put it in the contentPane of the JApplet
                    getContentPane().add(simpleAnimation);
                    setSize(simpleAnimation.getPreferredSize());
        catch (InterruptedException e)
            e.printStackTrace();
        catch (InvocationTargetException e)
            e.printStackTrace();
}Here's a 3rd bonus class that shows how to put the JPanel into a stand-alone program, a JFrame. It's very similar to doing it in the JApplet:
AnimationFrame.java
import javax.swing.JFrame;
public class AnimationFrame
    private static void createAndShowUI()
        JFrame frame = new JFrame("SimpleAnimationPanel");
        frame.getContentPane().add(new SimpleAnimationPanel());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    public static void main(String[] args)
        java.awt.EventQueue.invokeLater(new Runnable()
            public void run()
                createAndShowUI();
}Edited by: Encephalopathic on Mar 15, 2008 11:01 PM

Alternative to Double-Buffered Canvas

I am working on a program in which I use a double-buffered Canvas inside a JScrollPane. The problem is that the Canvas draws over the scrollbars. I have tried extending JComponent, JPanel, JApplet, and Component instead of Canvas, and none of them are double buffered. Here is the code I used to debug this problem:
import java.awt.*;
import java.awt.geom.*;
import java.awt.image.*;
import javax.swing.*;
public class Test implements Runnable
     JFrame f;
     JScrollPane scroller;
     JPanel panel;
     TestCanvas canvas;
     Thread runner;
     BufferStrategy strategy;
     public static void main (String[] args) {
          Test app = new Test();
          app.init();
     public void init() {
          f = new JFrame();
          f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          panel = new JPanel();
          canvas = new TestCanvas();
          panel.add(canvas);
          scroller = new JScrollPane(panel);
          scroller.setWheelScrollingEnabled(true);
          f.getContentPane().add(scroller);
          f.pack();
          f.setSize(300,300);
          f.setVisible(true);
          canvas.createBufferStrategy(2);
          strategy = canvas.getBufferStrategy();
          runner = new Thread(this);
          runner.run();
     public void run() {
          int x = 0;
          while(x != 65536) {
               Graphics2D g = (Graphics2D)strategy.getDrawGraphics().create();
               g.setColor(new Color(x%256,0,0));
               g.fill(new Ellipse2D.Double(0,0,600,600));
               strategy.show();
               x++;
}Any suggestions?

The main culprit is that you are mixing AWT components with Swing ones.
In addition, your are doing so many of useless things and wrong things in your code.
Swing components are defaulted for using double-buffering.
See: http://java.sun.com/products/jfc/tsc/articles/painting/index.html
Try and study this code.
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.*;
import javax.swing.*;
public class Fox1229{
JFrame f;
JScrollPane scroller;
TestCanvas canvas;
int x;
Timer t;
public static void main (String[] args) {
    Fox1229 app = new Fox1229();
    app.init();
public void init() {
    x = 0;
    f = new JFrame();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    canvas = new TestCanvas();
    scroller = new JScrollPane(canvas);
    scroller.setWheelScrollingEnabled(true);
    f.getContentPane().add(scroller, BorderLayout.CENTER);
    f.setSize(300, 300);
    f.setVisible(true);
    t = new Timer(50, new ActionListener(){
      public void actionPerformed(ActionEvent e){
        canvas.setOc(new Color(x % 256, 0, 0));
        canvas.repaint();
        if (++x == 1024){
          t.stop();
    t.start();
class TestCanvas extends JPanel{
Color oc;
public TestCanvas (){
    oc = new Color(0, 0, 0);
public void setOc(Color c){
    oc = c;
public Dimension getPreferredSize(){
    return new Dimension(600, 600);
public void paintComponent(Graphics g){
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D)g;
    g2d.setColor(Color.blue);
    g2d.fill(new Rectangle(0, 0, 600, 600));
    g2d.setColor(oc);
    g2d.fill(new Ellipse2D.Double(0, 0, 600, 600));
}

Using 6533 DIO32HS, is it possible to use double buffered output with varying pauses?

I'm using Level-Ack handshaking to transmit data. Currently, I'm hooked up to a loop-back on the DIO32HS card.
If I don't use double-buffering, I end up with pauses in data transmission, so I need to use double buffering. Unfortunately, I can't seem to set up a delay in the middle of a double buffered scheme.
What I need to do is this:
Transmit 64 packets of data (16 bits each) on group 2 / Receive 64 packets of data (16 bits each) on group 1
Delay for .2 ms
Transmit the same packets again / receive
The delay in the middle will need to be varied, from .2 to 20 ms.
I'm programming in Visual C++ 6.0 under Windows 2000, with (as suggested above) group1 c
onfigured as input (DIOA and DIOB) and group2 set up as output (DIOC and DIOD). Due to the speed of transmission (256kHz) and the small size of the data set, the program I wrote, no matter how tight I try to make it, cannot insert the proper delay and start the next send on time.
Does anyone have any idea if such a pause is possible? Anyone know how to do it, or any suggestions on what to try?
Thanks!

.2 ms is a very small time delay to use in software. Windows usually isn't more accurate than about 10 or 20 ms. If you need to have small, precise delays you could either use a real time OS, like pharlap and LabVIEW RT, or use extra hardware to generate the delays correctly.
I would recommend using a separate MIO or counter/timer board (like a 660x) to generate timing pulses for the DIO32HS. This gives you precise timing control at high speed. If the 32HS is in Level ACK Mode, it will respond to external ACK and REQ signals. This is covered in more detail on page 5-10 of the PCI-DIO32HS User Manual.

Double buffering still gives flickering graphics.

I copied code from a tutorail which is supposed to illustrate double buffering.
After I run it, it still flickers though.
I use applet viewer, which is part of netbeans to run my applet.
Link to tutorial: http://www.javacooperation.gmxhome.de/TutorialStartEng.html
My questions are:
Is the strategy used for double buffering correct?
Why does it flicker?
Why does the program change the priority a couple of times?
Can you make fast games in JApplets or is there a better way to make games? (I think C++ is too hard)
Here is the code:
package ballspel;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.JApplet;
//import java.applet.*;
* @author Somelauw
public class BallApplet extends /*Applet*/ JApplet implements Runnable {
private Image dbImage;
private Graphics dbg;
private int radius = 20;
private int xPos = 10;
private int yPos = 100;
* Initialization method that will be called after the applet is loaded
* into the browser.
@Override
public void init() {
//System.out.println(this.isDoubleBuffered()); //returns false
// Isn't there a builtin way to force double buffering?
// TODO start asynchronous download of heavy resources
@Override
public void start() {
Thread th = new Thread(this);
th.start();
public void run() {
Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
while (true) {
xPos++;
repaint();
try {
Thread.sleep(20);
} catch (InterruptedException ex) {
ex.printStackTrace();
Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
@Override
public void paint(Graphics g) {
super.paint(g);
//g.clear();//, yPos, WIDTH, WIDTH)
g.setColor(Color.red);
g.fillOval(xPos - radius, yPos - radius, 2 * radius, 2 * radius);
@Override
public void update(Graphics g) {
super.update(g);
// initialize buffer
if (dbImage == null) {
dbImage = createImage(this.getSize().width, this.getSize().height);
dbg = dbImage.getGraphics();
// clear screen in background
dbg.setColor(getBackground());
dbg.fillRect(0, 0, this.getSize().width, this.getSize().height);
// draw elements in background
dbg.setColor(getForeground());
paint(dbg);
// draw image on the screen
g.drawImage(dbImage, 0, 0, this);
// TODO overwrite start(), stop() and destroy() methods
}

Somelauw wrote:
I copied code from a tutorail which is supposed to illustrate double buffering.
After I run it, it still flickers though.
I use applet viewer, which is part of netbeans.. AppletViewer is part of the JDK, not NetBeans.
..to run my applet.
Link to tutorial: http://www.javacooperation.gmxhome.de/TutorialStartEng.html
Did you specifically mean the code mentioned on this page?
[http://www.javacooperation.gmxhome.de/BildschirmflackernEng.html]
Don't expect people to go hunting around the site, looking for the code you happen to be referring to.
As an aside, please use the code tags when posting code, code snippets, XML/HTML or input/output. The code tags help retain the formatting and indentation of the sample. To use the code tags, select the sample and click the CODE button.
Here is the code you posted, as it appears in code tags.
package ballspel;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.JApplet;
//import java.applet.*;
* @author Somelauw
public class BallApplet extends /*Applet*/ JApplet implements Runnable {
    private Image dbImage;
    private Graphics dbg;
    private int radius = 20;
    private int xPos = 10;
    private int yPos = 100;
     * Initialization method that will be called after the applet is loaded
     * into the browser.
    @Override
    public void init() {
        //System.out.println(this.isDoubleBuffered()); //returns false
        // Isn't there a builtin way to force double buffering?
        // TODO start asynchronous download of heavy resources
    @Override
    public void start() {
        Thread th = new Thread(this);
        th.start();
    public void run() {
        Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
        while (true) {
            xPos++;
            repaint();
            try {
                Thread.sleep(20);
            } catch (InterruptedException ex) {
                ex.printStackTrace();
            Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
    @Override
    public void paint(Graphics g) {
        super.paint(g);
        //g.clear();//, yPos, WIDTH, WIDTH)
        g.setColor(Color.red);
        g.fillOval(xPos - radius, yPos - radius, 2 * radius, 2 * radius);
    @Override
    public void update(Graphics g) {
        super.update(g);
        // initialize buffer
        if (dbImage == null) {
            dbImage = createImage(this.getSize().width, this.getSize().height);
            dbg = dbImage.getGraphics();
        // clear screen in background
        dbg.setColor(getBackground());
        dbg.fillRect(0, 0, this.getSize().width, this.getSize().height);
        // draw elements in background
        dbg.setColor(getForeground());
        paint(dbg);
        // draw image on the screen
        g.drawImage(dbImage, 0, 0, this);
    // TODO overwrite start(), stop() and destroy() methods
}Edit 1:
- For animation code, it would be typical to use a javax.swing.Timer for triggering updates, rather than implementing Runnable (etc.)
- Attempting to set the thread priority will throw a SecurityException, though oddly it occurs when attempting to set the Thread priority to maximum, whereas the earlier call to set the Thread priority to minimum passed without comment (exception).
- The paint() method of that applet is not double buffered.
- It is generally advisable to override paintComponent(Graphics) in a JPanel that is added to the top-level applet (or JFrame, or JWindow, or JDialog..) rather than the paint(Graphics) method of the top-level container itself.
Edited by: AndrewThompson64 on Jan 22, 2010 12:47 PM

Double buffering && repaint

Hi there,
I have a frame F that contains two panels P1 and P2.
P1 uses double buffering for drawing circles and lines.
P2 has buttons and a JList.
When i click on a JList to have popup menu
or when i move the frame F on the screen
the panel P2 lost some of JList drawing.
Actually i iconify the frame in order to oblige
JVM to do repaint.
How can i resolve this problem please.

Do not ever mix heavyweight and lightweight, or else
you won't be able to set up the correct zorder.But when i iconfiy and desiconify my frame Java
repaint correctly.
I need a nice tip article of how to simulate
desiconify repainting process.
Thabk u

Double buffering images

HELP!!! lol i'm trying to figure out how to get the whole double buffering thing to work with a picture like a gif image i drew in paint. i can't quite understand anything aobut how to do it. lol i've read some things and looked at some code samples but they all do it with a polygon. i just can't seem to get it right. i learn best from code snipets if that helps. don't give me a whole program i just want some lines that will help me learn it like what i have to import. and other things. i know a little about using images but not a whole lot. if anyone can help it will be appreciated.
andy

Psst... Tell you teacher that one can read an image with ImageIO, often in one line:
BufferedImage image = ImageIO.read(file_or_url_or_inputstream);(No need for a MediaTracker!) And the resulting BufferedImage (a subclass of Image)
is easier to work with than Image and has more useful features.
Welcome to Java 2D.

Double buffering... +1

Hi there......
Ive created a game that uses double buffering...basically the user hits the ball that is moving around the screen... after 5 goes the program needs to display a graph....
I have got the two components working seperatly... but when i combine that classes into one (the graph + the game) when theg graph is displayed the screen flickers..... and u cant see the graph properly....
How do you stop the screen from trying to keep refreshing and display the final image? (which is no longer animated)
Many thanks....

search this site or google
there are hundreds of posts about double buffering

Double buffering daqmx

I understand that DAQmx is supposed to do double buffering automatically. When I run the example below in continuous mode, It will run continuously without error. when I hit stop, it will give me a "Not enough memory to complete this operation." error. This error occurs only when i've acquired greater than about 70M samples. If I don't hit stop it will run to about 300M samples, give the above error and also an unspecified Labview error. The rate does not appear to affect this. Am I actually double buffering?
Does it only do double buffering with the "Continuous Samples" mode? I've been using the example below with both continuous and finite samples and in both cases it seems to acquire more samples the 64MB.
Does this have anything to do with what i'm seeing?
http://digital.ni.com/public.nsf/allkb/7DF86CA91D739AD386256DF900785211
Equipment:
Labview 8.2
NI-8350 Controller
MXI-4
PXI-6534

You are creating the second buffer in your application. DAQmx is not at fault here. You are wiring the output from the DAQmx Read VI to an auto-index tunnel on the While Loop. As your program runs this auto-index tunnel builds an array of every value that was sent to it in every iteration of the loop. So as time goes on, this array gets bigger and bigger. Eventually you will run out of available memory.
You should look into other ways of streaming data out of a loop, such as using Queues. You could then have a background loop to handle any data analysis or display.
Jarrod S.
National Instruments

Strange double buffering bug

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